2 results
Search Results
Now showing 1 - 2 of 2
- ItemThiophene-Bridged Donor–Acceptor sp2-Carbon-Linked 2D Conjugated Polymers as Photocathodes for Water Reduction(Weinheim : Wiley-VCH, 2021) Xu, Shunqi; Sun, Hanjun; Addicoat, Matthew; Biswal, Bishnu P.; He, Fan; Park, SangWook; Paasch, Silvia; Zhang, Tao; Sheng, Wenbo; Brunner, Eike; Hou, Yang; Richter, Marcus; Feng, XinliangPhotoelectrochemical (PEC) water reduction, converting solar energy into environmentally friendly hydrogen fuel, requires delicate design and synthesis of semiconductors with appropriate bandgaps, suitable energy levels of the frontier orbitals, and high intrinsic charge mobility. In this work, the synthesis of a novel bithiophene-bridged donor–acceptor-based 2D sp2-carbon-linked conjugated polymer (2D CCP) is demonstrated. The Knoevenagel polymerization between the electron-accepting building block 2,3,8,9,14,15-hexa(4-formylphenyl) diquinoxalino[2,3-a:2′,3′-c]phenazine (HATN-6CHO) and the first electron-donating linker 2,2′-([2,2′-bithiophene]-5,5′-diyl)diacetonitrile (ThDAN) provides the 2D CCP-HATNThDAN (2D CCP-Th). Compared with the corresponding biphenyl-bridged 2D CCP-HATN-BDAN (2D CCP-BD), the bithiophene-based 2D CCP-Th exhibits a wide light-harvesting range (up to 674 nm), a optical energy gap (2.04 eV), and highest energy occupied molecular orbital–lowest unoccupied molecular orbital distributions for facilitated charge transfer, which make 2D CCP-Th a promising candidate for PEC water reduction. As a result, 2D CCP-Th presents a superb H2-evolution photocurrent density up to ≈7.9 µA cm−2 at 0 V versus reversible hydrogen electrode, which is superior to the reported 2D covalent organic frameworks and most carbon nitride materials (0.09–6.0 µA cm−2). Density functional theory calculations identify the thiophene units and cyano substituents at the vinylene linkage as active sites for the evolution of H2. © 2020 The Authors. Advanced Materials published by Wiley-VCH GmbH
- ItemFreestanding Nanolayers of a Wide-Gap Topological Insulator through Liquid-Phase Exfoliation(Weinheim : Wiley-VCH, 2021) Lê Anh, Mai; Potapov, Pavel; Wolf, Daniel; Lubk, Axel; Glatz, Bernhard; Fery, Andreas; Doert, Thomas; Ruck, MichaelThe layered salt Bi14Rh3I9 is a weak three-dimensional (3D) topological insulator (TI), that is, a stack of two-dimensional (2D) TIs. It has a wide non-trivial band gap of 210 meV, which is generated by strong spin-orbit coupling, and possesses protected electronic edge-states. In the structure, charged layers of (Formula presented.) (Bi4Rh)3I]2+ honeycombs and (Formula presented.) Bi2I8]2− chains alternate. The non-trivial topology of Bi14Rh3I9 is an inherent property of the 2D intermetallic fragment. Here, the exfoliation of Bi14Rh3I9 was performed using two different chemical approaches: (a) through a reaction with n-butyllithium and poly(vinylpyrrolidone), (b) through a reaction with betaine in dimethylformamide at 55 °C. The former yielded few-layer sheets of the new compound Bi12Rh3I, while the latter led to crystalline sheets of Bi14Rh3I9 with a thickness down to 5 nm and edge-lengths up to several ten microns. X-ray diffraction and electron microscopy proved that the structure of Bi14Rh3I9 remained intact. Thus, it was assumed that the particles are still TIs. Dispersions of these flakes now allow for next steps towards the envisioned applications in nanoelectronics, such as the study of quantum coherence in deposited films, the combination with superconducting particles or films for the generation of Majorana fermions, or studies on their behavior under the influence of magnetic or electric fields or in contact with various materials occurring in devices. The method presented generally allows to exfoliate layers with high specific charges and thus the use of layered starting materials beyond van der Waals crystals. © 2020 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH